Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH 08/21] KEYS: Add signature verification facility [ver #3] | Date | Wed, 18 Jan 2012 12:26:23 +0000 |
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Kasatkin, Dmitry <dmitry.kasatkin@intel.com> wrote:
> It would also nice to have an API to supply pre-computed data hash. For > example IMA uses the same functionality to compute the hash of the file > content, and then, based on security.ima type decided either verify it using > just hash, or use digital signature. We could pass a hash as data. But may > be we do not want to have extra operation and compute hash over hash.
If I understand you correctly, you'd like to have the option to do the hashing externally to this API? Would you supply the completed hash or just a hash with the data in it, and require this API to complete it (ie. chuck metadata into it)?
I don't think it should be hard. I could add an alternative to verify_sig_add_data() perhaps. Either that or one function that does the lot and takes the precomputed hash as input. There would be no need for the split into four functions (begin, add_data, end, cancel) in such a case. The reason for the split is so that the caller can invoke add_data several times with non-contiguous bits of data.
It might even make sense to expose the crypto hash object for direct access rather than use add_data - but that then makes it hard to use crypto hardware where you would just shovel the raw data into it and it does all the hashing and cryptography in a black box.
David
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